1. Field of the Invention
The invention relates to a device for determining the high-voltage potential on the high-voltage conductor of a metal-encapsulated high-voltage switching installation wherein the high-voltage conductor is supported by the grounded encapsulation of the installation by bodies of insulating material.
2. Description of the Prior Art
Measuring devices of the above type are known in the prior art. Such devices typically include an electrode which is arranged between and insulated from the high-voltage conductor and the grounded encapsulation and which generates a signal for a measuring circuit. In particular, such an electrode can serve as the high-potential capacitor of capacitive voltage divider. In a somewhat different arrangement of this kind, the signal from the electrode is used to control the on-off position of an electric switch gear arranged within the encapsulation.
In either case, an interruption of the line carrying the electrode signal to the measuring circuit leads to faulty information which, while undesirable, is permissible for voltage measurement, but is not permissible for voltage checking, which is used to ensure the safety of the maintenance and operating personnel of the switching installation. More particularly, in the case of a capacitive voltage divider system, a fault in the form of a line interruption leads to an incorrect signal regarding the operating condition. Moreover, in a switch position-indicating system, the electrode and the measuring circuit cannot be readily designed so that an interruption of the signal transmission line leading from the electrode can be recognized unequivocally in the measuring circuit. Thus, if the switch is a grounding switch and the electrode signal lifts or puts in operation the necessary interlock, no unequivocal statement regarding the presence of a high-voltage potential can be obtained in the case of a line interruption without further tests being taken. In VDE Specification 0105 Part 1, Item 7, several tests must be carried out to establish and ensure the voltage-free condition prior to the start of work and acceptance of the work.
It is an object of the present invention to provide an improved high-voltage measuring device of the above-type.